Lubricating oil and method of protecting same



FIFE-G? Zelzlg-fi UNITED s'rrcrss PATENT OFFICE LUBRICATING OIL AND METHOD OF PROTECTING SAME No Drawing. Application August 1, 1936, Serial No. 93,761

8 Claims.

This invention is directed to highly refined lubricating oils, stable against the deteriorating efiects of oxidation under normal conditions of use.

Highly refined lubricating oils, of the nature of turbine oils, white oils, and the like, prepared by treatment with relatively large amounts of sulphuric acid, or of fuming sulphuric acids, or by methods of solvent refining, as with liquid sulphur dioxide, and the like, designed to produce a finished oil of the same nature, are notably prone to deterioration due to the effects of oxidation reactions, under their normal conditions of use at elevated temperatures, particularly when in contact with metals. This oxidation results in the formation of acidic products, which decrease the insulating or, dielectric strength of the oil and lessen its usefulness in such applications as transformers, electrical cables, and the like, and are of a corrosive and objectionable nature when it is used for lubrication, as in turbines.

This invention has for its object the provision of, a highly refined oil substantially stable against oxidation under normal conditions of use, a method of protecting such oils against oxidation, and such other objects as will hereinafter appear.

This invention is based upon the discovery that such an oil may be substantially stabilized against the deteriorating effects of oxidation reactions by incorporating therein a small amount of a member of the group of organic compounds designated as the alkyl esters of alkyl xanthates.

The alkyl esters of alkyl xanthates are products which may be prepared by reacting alkyl halides with alkali salts of alkyl xanthic acids, which latter have been prepared by reacting an alcohol, carbon disulphide, and caustic alkali. The typical reactions involved are as follows:

ROSCSK being the alkali salt of the xanthic acid of the alkyl R.

Wherein X is a halogen, and ROSC'SR is the ester of the alkyl R and of the alkyl xanthic acid ROSCSH.

In the above type reactions R and R may be the same or different alkyls or aralkyls. For example, they may be selected from the group consisting of:

methyl lauryl ethyl cetyl propyl oleyl butyl stearyl amyl benzyl hexyl phenyl ethyl heptyl etc.

Of this group of alkyls and aralkyls it is preferred to use the relatively simple alkyls and aralkyls as ethyl, amyl, propyl, butyl, benzyl and the like.

cili-iii'ibiii W Also among the alkyl esters of. alkyl xanthates I include the dialkyl xanthates which might be designated as alkylene di esters of alkyl xanthates. These are formed from a dihalogen compound as follows:

noscsx X--R" ROSCS-R RoscsKi x-r v" ROSCS-J-V" R" and R being any suitable alkylene residue such as methylene, propylene, butylene, etc.

The method of preparation is that of reacting together the alcohol containing the desired alkyl thate, and the propylene ester of. n-butyl xan thate.

The stability of a highly refined oil toward oxidation may be conveniently tested by heating 150 grams of it to 120 C., and bubbling oxygen gas through it at a rate of 2 liters per hour for 70 hours. ucts is then determined by titrating with caustic alkali and is expressed by the neutralization number, (milligrams of KOH required to neutralize acids in 1 gram of oil).

The following tabular data show the compara- The amount of acidic oxidation prodtive results obtained when an oil of specific gravity 0.87, Lovibond color less than 0.1 and viscosity of 69 Saybolt Universal at F. was tested as above, alone and also in admixture with the specified amounts of certain of the novel stabilizers herein disclosed, as described in the left-hand column of the table.

Neut. number after test JJH SCSO C211 Oil+.l0% ethylene diester of iso-arnyl xanthate 06 GHQSOSOC5H11 I GHQ-80800 11 Oil-5.10% propylene diester ol n-butyl xanthate 03 co H0 coco fiai o It will be seen from the above data that the novel stabilizing compounds herein disclosed, viz., the alkyl esters of alkyl xanthates, possess to a high degree the capability of inhibiting the deteriorating efiect of oxidation upon highly refined mineral lubricating oils. It will be noted that the percentages of the inhibitive compound used is quite low, substantial inhibition being obtained in the case of most of the compounds of this class with the use of only 0.10% of the inhibitive ingredient. Proportions of these compounds to be mixed in oil to accomplish the purposes of this invention will range from about 0.10% to not over 0.50%, the lower percentages being preferable.

In the claims, the term highly refined lubricating oil means an oil of the nature of white oils, turbine oils, and the like, generally nonsludging, produced by refining with a relatively high amount of sulphuric acid, or by other agents capable of producing a similar degree of refinement, without regard to the use of the oil, whether it be as a lubricant or as a dielectric.

I claim:

1. A mineral oil composition comprising a highly refined lubricant oil and incorporated therein a small amount, not to exceed 0.5 per cent and suflicient only to stabilize against oxidation, of an alkyl ester of an alkyl xanthic acid.

2. A lubricating oil composition, highly stable against the deteriorating efiect of oxidation reactions, comprising a highly refined petroleum lubricant oil and a small amount, not to exceed 0.5 per cent and sufi'icient only to stabilize against oxidation, of a compound selected from the group consisting of the alkyl and dialkyl esters of alkyl and aralkyl xanthic acids.

3. An oil composition, highly stable against the formation of acidic products by oxidation re action, comprising a highly refined petroleum oil fraction of high boiling point which is not so stable, and in admixture therewith a small amount, not to exceed 0.5 per cent and sufficient only to stabilize against oxidation, of a substance characterized by the presence of the grouping ROSCSR, where R is an alkyl radical.

4. An oil composition highly stable against the formation of acidic products of oxidation, comprising a highly refined petroleum oil fraction of high boiling point not so stable, and in admixture therewith a small amount, not to exceed 0.5 per cent and sufiicient only to stabilize against oxidation, of a compound selected from the group consisting of ethyl ester of ethyl xanthate, n-amyl ester of iso-amyl xanthate, benzyl ester of iso-amyl xanthate, n-amyl ester of benzyl xanthate, benzyl ester of iso-propyl xanthate, ethylene diester of ethyl xanthate, ethylene diester of iso-amyl xanthate, and propylene diester of n-butyl xanthate.

5. An oil composition, highly stable against the formation of acidic products by oxidation reaction, comprising a highly refined petroleum oil fraction of high boiling point which is not so stable, and in admixture therewith a small amount, not to exceed 0.5 per cent and sufficient only to stabilize against oxidation, of a compound selected from the group consisting of: alkyl esters of alkyl xanthic acids, aralkyl esters of alkyl xanthic acids, and alkyl esters of aralkyl xanthic acids.

6. An oil composition, highly stable against the formation of acidic products by oxidation reaction, comprising a highly refined petroleum oil fraction of high boiling point which is not so stable, and in admixture therewith a small amount, not to exceed 0.5 per cent and sufficient only to stabilize against oxidation, of a substance characterized by the presence of the grouping ROSCSR', where R and R represent radicals selected from the group consisting of alkyl and aralkyl radicals.

7. An oil composition, highly stable against the formation of acidic products by oxidation reaction, comprising a highly refined petroleum oil fraction of high boiling point which is not' so stable, and in admixture therewith a small amount, not to exceed 0.5 per cent and sulficient only to stabilize against oxidation, of a substance characterized by the presence of the grouping ROSCSR, Where R and R" represent radicals selected from the group consisting of ethyl, propyl, butyl, amyl, hexyl, and benzyl radicals.

8. An oil composition, highly stable against the formation of acidic products by oxidation reaction, comprising a highly refined petroleum oil fraction of high boiling point which is not so stable, and in admixture therewith a small amount, not to exceed 0.5 per cent and sufficient only to stabilize against oxidation, of a compound characterized by the general formula:

in which R represents a radical selected from the group consisting of alkyl and aralkyl radicals, R" and R' being an alkalene residue.

EVERETT W. FULLER. 

